High pressure spectroscopic study of ferricenium hexafluorophosphate: Pressure-induced order-disorder transitions

Abstract

Studies of the visible and infrared spectra of polycrystalline ferricenium hexafluorophosphate show discontinuities near 5 kbar. These changes are attributed to an order-disorder phase transition, which has also been observed at 211 K (atmospheric pressure). A volume decrease of 1.66 cm 3 mol −1 has been calculated for this transition, which is significantly less than that for the order-disorder transition which occurs at 347 K. It is proposed that the transition studied here involves at the very least an orientational change for Fe(cp) 2 + on the basis of large changes in the spectroscopic features assignable to the cation.